I'm usually on medic so you would think that I wouldn't like crits, however, I don't mind them at all. Not only does it throw another factor in the mix up, but it may allow someone new to the game get a kill easier. There are some days that I just loathe crits though....its those days when I'll get death after death because of them and lose ubers.
and also @doomcat
but that's the thing, random chance really reduces strategy
can you imagine a lucky kill like that in quake 3? absolutely not! Can you imagine a new player taking out an experienced sc gamer. never. That;s why those games are pro, pure skill, pure strategy
granted, they are 1v1 games, but if we take 1.6, the only lucky kill I can think of is lucky headshot from spraying by a noob. Regardless, it's all about coordination, so while there is a tiny bit of luck, a new player would never take down an experienced one (though I'm not big on cs, don;t play it as much, but my friend taught me a few things though)
that's what defines a game as pro, a new player can never take out an experienced one, maybe only through beginners luck, but that doesn't relate to any mechanic within the game, especially so obvious as random insta-kill hits (basically)
perhaps my argument is elitist, but games should cater to pros and hardcore crowd, crits obviously there to cater to noobs as doomcat pointed out, so yeah. Not a big fan of random uncontrollable crits
control is also another thing, but maybe I'll talk about that when I'm less sleepy
edit: on second thought, that's not really a problem with tf2 in particular, but with modern gaming in general